Huh? This is Chase Field:
Basically, Chase Field : Fenway Park :: Phoenix : Boston.
First off, most (all?) of these parks are younger than the buildings around them. I think the oldest one posted above is 80 years (!) Fenway's junior.
Also, most (all?) of these parks do not have buildings as close to them as tall as 2 Charlesgate would be to Fenway. The buildings in the backgrounds of many of these shots are more in Back Bay High Spine category as far as distance and prominence, and the Sox have no problem with those.
But most importantly, Fenway is not other parks. Saying that there's no difference between Fenway and Chase Field is like saying that there's no difference between the Chrysler Building and One Beacon Street. You know that Fenway is not like these other ballparks because it is still standing after 100+ years, while all these other parks opened in the Clinton Administration or later. If Fenway were like these parks, it would have been torn down decades ago. The only other park in the same category as Fenway is Wrigley, and you can be guaranteed that if a building like 2 Charlesgate were proposed in the same location relative to Wrigley it would hit the same opposition or worse. If you don't understand the difference go read up a bit on baseball park architecture--this is an architecture forum after all--and on Fenway's place in baseball, and American, history.
This isn't to say that 2 Charlesgate should be stopped. There's a very solid argument that the powers-that-be should hear the Red Sox' argument and then go ahead give the project their approval none-the-less. But to say that other stadiums have buildings near them so nobody should care what gets built near Fenway is ignorant and disingenuous. The relative merits of the Red Sox opposition can be debated, but that doesn't mean it has "no merit". And I have no data to base this on, but my hunch is that many more people in this city and state would side with the Red Sox on this one than with Belkin.
Externalities are externalities, even if you don't particularly care for the party that is affected.